Burner control device for a water heater



June 3, i969 C- D- WS05 3,447,746

BURNER CONTROL DEVIC FOR A WATER HEATER Filed 001;. 17, 196

United States Patent O 3,447,746 BURNER CONTROL DEVICE FOR A WATER HEATER Charles D. Visos, St. Louis, Mo., assignor to Emerson Electric Co., St. Louis, Mo., a corporation of Missouri Filed Oct. 17, 1966, Ser. No. 587,203 Int. Cl. GOSd 23/22; F23n 5/10 U.S. Cl. 236-21 4 Claims This invention relates to automatic fuel flow control devices for water heater gas burners which include a temperature responsive valve for controlling gas flow to the burner in accordance with requirements to maintain a preselected water temperature and an electromagnetic, manually resettable, cutoff valve dependent upon electrical energy generated by a pilot burner-heated thermocouple to hold it in a set open position. More particularly, the invention concerns the provision of a novel, economical, and compact unitary construction incorporating a screw threaded means for a-ttaching the control device to a water tank, rod and tube type thermostatic means extending axially therefrom for actuation of the temperature responsive valve, and high temperature limit switch means for controlling the thermocouple energizing circuit of the electromagnetic cutoff valve.

An object of the invention is to provide a rod and tube type thermostat for insertion into a water tank in which the tube member is formed as an integral extension of an exteriorly supported control casing member by casting from a relatively inexpensive metal having a high coeicient of thermal expansion, such as aluminum, and in which the tube portion is provided with a thin-walled, press tted sheath including a thickened, externally threaded, base attaching portion formed of relatively expensive metal having a high coefficient of thermal expansion and high resistance to the corrosive effects of hit tap water, such as copper.

A further object is to provide a unitary construction comprising a rod and tube type thermostat and a high temperature limit switch, comprising a bimetal actuator and switch contacts, mounted in a chamber formed as a cavity at the outer end of the rod and tube thermostat.

Other objects and advantages will appear from the following description when read in connection with the accompanying drawing.

In the drawing:

FIG. l is a longitudinal cross-sectional view of a fuel flow control device for water heater gas burners constructed in accordance with the present invention, the device being shown in association with a fragmentary portion of a water heater tank;

FIG. 2 is a longitudinal cross-sectional view of the electromagnetic cutoff valve with its circuit connections;

FIG. 3 is an enlarged cross-sectional view taken on line 3-3 of FIG. 1;

FIGS. 4 and 5 are enlarged, fragmentary, longitudinal sectional views of the outer end portion of the rod and tube thermostat showing the high temperature limit switch sectionailized and in closed and open positions respectively; and

FIG. 6 is a detail plan View of the movable contact ring and blade of the high temperature limit switch.

Referring to FIG. l of the drawing, the fuel flow control device comprises a valve body 10 having front and rear cover members 12 and 14, respectively, attached to the body 10 by screws 16. The body 10 is provided with a fuel inlet passage 18, a cutoff valve chamber 20, a main valve chamber 22, and a main fuel supply outlet passage 24. A tapered bore 26 and an axially aligned cylindrical bore 28 extend inwardly from opposite sides of body 10 and intersect the cutoff valve chamber 20. The tapered bore 26 receives a hollow, tapered, rotatable plug cock 30, the open inner end of which extends into chamber 20 and forms an annular valve seat 32.

The cylindrical bore 28 receives an electromagnetic cutoff Valve assembly, generally indicated at 34, which includes a poppet valve 36 biased against valve seat 32 by a spring 13. An operating rod 11 axially slidable in plug cock 30 and having an external hand knob 17 is arranged to engage cutoff valve 36 and move it openward when knob 17 is pushed inward manually. The operating rod 11 and knob 17 are biased outwardly by spring 19.

The hollow plug cock 30 is provided with a circumferentially extending groove in the outer wall thereof and a port 38 which permits flow from the interior of the plug cock to a pilot burner outlet passage 40 from whence fuel is conducted to a pilot 'burner 43 through a conduit 41. The plug cock 30 is also provided with a circular main port 42 in the wall thereof which, when in registry with a body passage 44, permits fuel flow from -the interior of the hollow plug cock to the main valve cham-ber 22,. The circumferentially extending groove at port 38 provides for rotatably positioning the plug cock -so as to permit the flow of fuel either to the pilot outlet 40 only or to the pilot outlet 40 and main valve chamber 22 simultaneously. A main poppet valve 46 biased in a closed position on an annular valve seat 48 by a spring 50 controls the ow from main valve chamber 22 to the main valve outlet passage 24.

The main valve 46 has a stem 52 extending therefrom through a guide bore 53 into a circular chamber 55, where its free end is engaged under certain conditions by the central portion of a1 thin, circular, concave-convex disc 54. The disc 54 has a normal free form position, as shown in FIG. 1, in which it is concave with respect to the adjacent end of valve stem 52. The disc 54 is poised between a fixed, annular, knife-edge member 56, which engages the disc on its concave side Very near its peripheral edge, and 4an annular knife edge 58 of slightly smaller diameter formed on the inner face of an axially slidable member 60, which engages the disc on its convex side. A slight inward movement of member '60 causes disc 54 to pass through a planar shape to an opposite concavo-convex form with a snap action and to engage the adjacent end of valve stem 52 and to open the valve 46.

The outer face of 4axially slidable member 60 is provided with a hemispherical boss 62 engaged by the free end of a lever 64, the lever 64 -being pivoted at its other end on the ball-shaped end 66 4of a -threadedly adjustable rod 68. The rod 68 is provided with a hand knob 70 on its exteriorly projecting end.

The rear cover member 14 is formed as a casting and includes an elongated, integral, hollow boss or tube portion 72 having an integral closure wall 74 near its outer end and a circular recess 76 formed by a circular wall extending outwardly beyond closure wall 74. The cover member 14 is constructed yof a relatively inexpensive metal, such as aluminum, having high heat conductivity and a high coeflicient of thermal expansion. The elongated hollow boss 72 forms the tube of a rod and tube thermostat |which further includes a rod 78 of -metal havof thermal expansion. The rod 78 is threadedly engaged at its outer end in a threaded bore through the tube closure wall 74. The outer end of rod 78 is slotted to receive a screw driver.

Press fitted into the circular recess 76 at the outer end of tube portion '72 is a cylindrical-shaped, temperature responsive switch unit generally indicated at 80. Referring t-o FIGS. 4 and 5, the switch 80 comprises a cupshaped main body member 81 of dielectric material, a stationary contact 82 attached to the inner bottom of body member 81 by a conductive rivet 83, a movable contact-carrying member generally indicated at 84, and a circular bimetal disc 85. The movable contact carrying member 84 consists of a ring portion 86, see FIG. 6, which overlies the rim of cup-shaped main body member 81, and a diametrically extending contact arm portion 87 which carries a contact 79 at its free end for cooperation with stationary contact 82. The contact carrying member 84 is constructed of spring bronze, and in its free form, the arm portion 87 biases movable contact 79 upward in contact with stationary contact 82, as shown in FIG. 4. The bimetal disc 85 overlies the ring portion of contact carrier 84, and the contact carrier 84 and bimetal disc 85 are retained in assembly with main body member 81 by a surrounding conductive sleeve 88 formed over at the top and bottom at 89 and 90, respectively.

At normal water temperatures, that is, below that predetermined to be a maximum safe temperature, the bimetal disc 85 assumes the concavo-convex form shown in FIG. 4, which permits the arm portion 87 to bias movable contact 79 upward against stationary contact 82. When the temperature of the bimetal disc attains or exceeds the predetermined safe maximum, it snaps through a planar shape to the opposite concave-convex form shown in FIG. 5 and, when doing so, engages contact arm 87 and bends it downward, thereby separating the contacts 82 and 79.

The circular cavity 76 is provided with a cover plate 91, and a relatively thin-walled closed end sleeve 92 is press fitted over the tube portion 72. The thin wall, closed end sleeve 92 is constructed of a metal or alloy, such as copper or brass, having good heat conductivity, a high coefficient of thermal expansion, and a high resistance to the corrosive effects of heated tap water. The sleeve 92 forms a protective sheath against erosion of the tube portion 72 and extends inwardly from the outer end of tube portion 72 and enters a counterbore in an externally threaded sleeve member 93 which is press fitted on the inner end of tube portion 72. The somewhat thickerwalled threaded sleeve 93 is also constructed of a metal or alloy having high resistance to the corrosive eiects of hot tap water. The wall of tube portion 72 is thickened near its junction with the at portion of cover member 14, and a square shoulder 94 is formed against which threaded sleeve 93 abuts. The inner end of threaded sleeve 93 is provided with one or more projecting tangs 95 which enter one or more notches formed in shoulder 94, thereby to key the sleeve 93 against rotation on tube portion 72. The junction of the open end of thin wall sleeve 92 and threaded sleeve 93 is sealed with a high temperature, thermosetting, synthetic plastic cement.

It will be understood that the thin Walled sleeve 92, the cavity cover disc 91, and the somewhat thicker walled, externally threaded sleeve 93 may be drawn and swaged from a suitable metal or alloy as a unitary member. The purpose of the cover disc 91 is to support the closed end of thin Walled tube 92 against deformation by high water pressure, therefore by thickening the closed end of sleeve 92 somewhat this cover disc may be dispensed with. Production of the device in suiciently large quantities would economically justify the expenditure for tooling required to draw and swage these three members as an integral unit and such construction is contemplated.

The externally threaded sleeve 93 is threadedly engaged in an internally threaded bushing 98 welded into an apering a low coelicient ture in the wall of a water heater tank, shown fragmentarily at 96 in FIG. 1, whereby the control device is supported on the water tank and the shielded tube portion 72 extends into the water tank. The rod 78 extends inwardly from its adjustably threaded connection to the closure Wall 74, through a guide hole in a plate 97 press fitted in a counterbore at the inner end of tube portion 72, and thence into the body 10 where the inner end thereof abuts an intermediate portion of lever 64.

An insulated electrical lead 112 connected at one end to stationary contact 82 through a terminal clip 102 and conductive rivet 83` extends therefrom through the tube portion 72 to its base and then outwardly through a transverse bore to a connection with electromagnetic valve 34. A clearance aperture 104 in wall 74 is provided for the passage of terminal clip 102 and lead 112.

Referring to FIG. 2, the electromagnetic cutoff valve assembly 34 comprises a cylindrical casing 100 which is connected at one end to a terminal plug generally indicated at 116. The other end of casing slidably supports a valve stem 118. Valve stem 118 carries the valve 36 on its exteriorly projecting end and an armature 15 on its interior end. The terminal plug 116 is provided with an enlarged diameter, threaded ange portion 120 which is threadedly engaged in a threaded bore 122 in cover 14. The casing 100 houses a U-shaped, electromagnetic core, generally indicated at 124, having a winding 126 surrounding its parallel leg portions 128. A conductive rivet 132 extends through a bore in the leg connection portion 130 of the magnet core, and through a bore 121 in terminal plug 116, and rigidly connects the core 124 to the terminal plug 116 mechanically but not electrically. The inner end of conductive rivet 132 is connected to one end of winding 126 at 131. A circular dielectric member 132 is interposed between the casing 100 and terminal plug 116, and the member 134 includes encased therein a conductor 136 having one end extending into casing 100 and being connected to the other end of winding 126 and having its other end extending exteriorly of the body 10 and being connected to the lead 112.

A thermocouple junction encased in a casing 138 is disposed with relation to pilot burner 43 so as to be impinged by the iiame thereof. Coaxial tube and wire conductors 140 and 141, respectively, lead from the thermocouple junction to terminal plug 116. The end portions of tube and wire conductors 140 and 141 pass through a hollow nut 143 which is threadedly engaged in an axial threaded bore 117. The tube conductor 140 has a dared end which bears against the inner end of nut 143, and the wire conductor 141 has an enlarged diameter contact element 142 at its end which bears against the inner end of conductive rivet 132. An insulating washer is interposed between the ared end of conductor tube 140 and the contact element 142. Dielectric grommets electrically insulate the conductive rivet 132 from the terminal plug 116 and the portion 130 of the magnet core.

The thermocouple-electromagnet circuit further includes in series connection the normally closed high temperature limit switch 80. The entire thermocouple-electromagnet circuit may be traced as follows: starting at the thermocouple junction in casing 138 the circuit eX- tends through conductor wire 141, contact element 142, conductive rivet 132, winding 126, conductor 136, lead 112, terminal clip 102, rivet 83, stationary contact 82, movable contact 79, contact arm 87, and rim portion 86, conductive sleeve 88, tube portion 72, cover 14, terminal plug 116, lhollow nut 143, and conductive tube 140 to the thermocouple junction in casing 13S.

From the foregoing it will be seen that a minimum amount of more expensive corrosion resistant copper or brass is employed and that the possibility of leakage is made remote than in conventional constructions wherein the tube of the rod and tube thermostat is a separate member screwed into the mounting boss. The possibility of leakage is made further remote when the thin-walled tube 92 and the thicker-walled, threaded, mounting sleeve are drawn and swaged as a single unit. It will also be seen that the high temperature limit switch 80 is positioned so as to be responsive to the highest water ternperature in the tank at a particular level, that is, it is near the burner flue which is usually centrally located. The cavity cover disc 91 and the end wall of sleeve 92, or in the case of an integrally formed unit, the end wall of the sleeve alone, need only be thick enough to withstand deformation by water pressure, and the bimetal disc 85 may be placed in close relationship with the end wall so as to be immediately responsive to water temperature change.

In the interest of simplicity of illustration the tube portion 72 is shown cast as an integral part of the entire rear cover member 14, which is attached to the main body member by screws 16. It may be found desirable in practice, however, to cast the tube portion 72 integral with a smaller auxiliary cover or flange portion adapted to be attached to a main rear cover member by screws. This latter arrangement simplifies casting and provides a unitary rod and tube thermostat and limit switch universally adaptable to valve bodies of different size and the use of this arrangement is contemplated.

When it is desired to start burner operation, the plug valve 30 is rotated to a pilot position which will permit fuel to ow from the hollow plug valve 30 to the pilot burner outlet 40, but will not permit ow through circular port 42 to chamber 22. The knob 17 is then pushed inward to open cutoff valve 36 and to move armature 15 into contact with the ends of magnet core legs 128. The pilot burner is then ignited by any suitable means, and knob 17 is held inward until electrical energy is generated at the thermocouple junction and sufficiently energizes winding 126 to hold the armature 15 against core 124 and the cutoff valve open. Thereafter, the plug cock 30 is rotated to an on position, in which fuel liows through port 42 to chamber 22 as well as through grooved port 38 to the pilot burner.

If the water temperature sensed .by the tube portion 72 of the rod and tube thermostat is less than that selected by the manual positioning of knob 70, the tube portion 72 will be in such contracted position as to cause rod 78, through lever 64, member 60, and snap disc 54, to open main valve 46. Fuel will thereby be permitted to flow to the main burner outlet 24 and thence to a main burner (not shown) where it is ignited by the pilot burner. When the water reaches the preselected temperature due to operation of the main burner, lengthwise expansion of tube portion 72 and its sheath 92 will effect withdrawal of rod 78 and permit disc element 54 to return to its normal free form, as shown, and will permit valve 46 to close under the bias of spring 50. Under normal conditions, the main valve 46 will now be operated between open and closed positions to supply fuel to the main burner as required to maintain the selected water temperature.

If, however, for any reason, the temperature of the water in the tank rises to or exceeds that which has been predetermined to be a safe upper limit, the bimetal disc 85 of limit switch 80 will snap to an opposite concavoconvex form, as shown in FIG. 5, and contacts 82. and 79 will be separated, thereby breaking the thermocoupleelectromagnet circuit. As a result, the winding 126 becomes de-energized and spring 13 returns valve 36 to a closed position, thereby cutting off the flow of fuel to both pilot and main burners.

The foregoing descritpion is intended to be illustrative and not limiting, the scope of the invention being set forth inthe appended claims.

I claim:

1. In a fuel flow control device for controlling gas flow to the gas burner of a water heater, which device is adapted to be mounted on the water tank by engaging a threaded boss on the device in a threaded aperture in the tank wall and which device has a rod and tube type thermostatic valve actuator adapted to be inserted into the water tank through the threaded wall aperture; the improvement which consists in providing a tube member for the thermostatic rod and tube valve actuator which also serves as a structural member to support the control device, the tube member being formed as a casting of relatively low cost metal having a relatively high coefl'lcient of thermal expansion but having relative low resistance to corrosion in heated tap water, the tube member comprising a flat cover portion connected to the body of the control device and (a) an integral tubular portion extending perpendicularly from said cover portion to a closed outer end and receiving a rod member, said tubular portion having an externally screw threaded bushing press tted thereon near the junction of its inner end with said cover portion, which bushing is adapted to be threadedly engaged in a screw threaded aperture in the wall of a water heater tank, and a thin protective sheath of material having a relatively high resistance to the corrosive effects of tap water tightly fitted on said tubular portion and extending from said threaded bushing to the outer end thereof and covering the end thereof, and said threaded bushing .being constructed of a relatively expensive metal having a high resistance to corrosion in hot tap water.

2. The improvement set forth in claim 1, in which said thin protective sheath is constructed of relatively expensive metal having a relatively high rate of heat conductivity and a high resistance to corrosion in hot tap water and being in continuous Contact with the wall of said tubular portion thereby to effect rapid heat transfer between the ambient water and the Wall of said tubular portion.

3. The improvement set forth in claim 1 in which said externally screw-threaded bushing and said thin protective sheath are formed integral.

4. In a flow control device for a water heater gas burner having a valve body through which ow is controlled by two series arranged valves, one being operated by a rod and tube thermostat adapted to be inserted into the water tank through a wall aperture and the other being a cutoff valve held open by an electromagnet, the energization of which is under the control of a high temperature limit switch responsive to excessively high water temperature to de-energize the electromagnet and cause the closing of the cutolf valve; the improvement which consists in providing a tube member for the rod and tube thermostat which includes a chamber at the outer end thereof for encasing the high temperature limit switch, the tube member being formed of metal having a relatively high coeicient of thermal expansion and having an inner open end with an integral flange at said inner open end for attaching the tube to said valve body, the tube having a closing wall spaced inwardly a short distance from its outer end to form a recess extending inwardly from said outer end, a rod having a relatively low coefficient of thermal expansion in said tube, said rod having one end thereof adjustably connected to said closing wall by threaded engagement therein and extending inwardly therefrom through said tube and into said valve body, a thermostatic high temperature limit switch in said recess including a circular bimetal disc actuator adjacent and facing the open end of said recess and including an electrical lead extending therefrom through an aperture in said closing wall and inwardly through said tube, and a relatively thin wall of high heat conductive material closing said outer end of said tube thereby to close said recess and enclose said limit switch in a chamber at the outer end of said tube.

(References on following page) References Cited UNITED STATES PATENTS Kenney 236-102 Meyer et al 236-102 X Kreuter.

Jackson et al.

Wadsworth 236-102 Boker 236-102 8 1,995,385 3/1935 Foote 236-102 X 2,583,236 1/1952 Spence 236-87 3,291,390 12/1966 Solomon.

5 EDWARD I. MECHAEL, Primary Examiner.

U.S. C1. X.R. 

1. IN A FUEL FLOW CONTROL DEVICE FOR CONTROLLING GAS FLOW TO THE GAS BURNER OF A WATER HEATER, WHICH DEVICE IS ADAPTED TO BE MOUNTED ON THE WATER TANK BY ENGAGING A THREADED BOSS ON THE DEVICE IN A THREADED APERTURE IN THE TANK WALL AND WHICH DEVICE HAS A ROD AND TUBE TYPE THERMOSTATIC VALVE ACTUATOR ADAPTED TO BE INSERTED INTO THE WATER TANK THROUGH THE THREADED WALL APERTURE; THE IMPROVEMENT WHICH CONSISTS IN PROVIDING A TUBE MEMBER FOR THE THERMOSTATIC ROD AND TUBE VALVE ACTUATOR WHICH ALSO SERVES AS A STRUCTURAL MEMBER TO SUPPORT THE CONTROL DEVICE, THE TUBE MEMBER BEING FORMED AS A CASTING OF RELATIVELY LOW COST METAL HAVING A RELATIVELY HIGH COEFFICIENT OF THERMAL EXPANSION BUT HAVING RELATIVE LOW RESISTANCE TO CORROSION IN HEATED TAP WATER, THE TUBE MEMBER COMPRISING A FLAT COVER PORTION CONNECTED TO THE BODY OF THE CONTROL DEVICE AND (A) AN INTEGRAL TUBULAR PORTION EXTENDING PERPENDICULARLY FROM SAID COVER PORTION TO A CLOSED OUTER END AND RECEIVING A ROD MEMBER, SAID TUBULAR PORTION HAVING AN EXTENALLY SCREW THREADED BUSHING PRESS FITTED THEREON NEAR THE JUCTION OF ITS INNER END WITH SAID COVER PORTION, WHICH BUSHING IS ADAPTED TO BE THREADEDLY ENGAGED IN A SCREW THREADED APERTURE IN THE WALL OF A WATER HEATER TANK, AND A THIN PROTECTIVE SHEATH OF MATERIAL HAVING A RELATIVELY HIGH RESISTANCE TO THE CORROSIVE EFFECTS OF TAP WATER TIGHTLY FITTED ON SAID TUBULAR PORTION AND EXTENDING FROM SAID THREADED BUSHING TO THE OUTER END THREROF AND COVERING THE END THEREOF, AND SAID THREADED BUSHING BEING CONSTRUCTED OF A RELATIVELY EXPENSIVE METAL HAVING A HIGH RESISTANCE TO CORROSION IN HOT TAP WATER. 